Four-axis micro-aircraft based on radial-bending composite ultrasonic motor

Abstract

The invention discloses a four-axis micro-aircraft based on a radial-bend composite sheet ultrasonic motor. Ultrasonic motors of special structure are respectively installed on the rotors of the aircraft. When the four-axis micro-aircraft is in a working state, the lifting, pitching, rolling, yaw and other functions of the aircraft can be realized by changing the magnitude of the voltage applied to four ultrasonic motors A, B, C and D, thereby changing the rotation speed of the rotating shaft.

Description

Technical Field

[0001] The invention relates to the field of ultrasonic motor technology and micro-aircraft, and in particular to a radial-bend composite sheet-shaped ultrasonic motor. Background Art

[0002] Most traditional micro quadrotor micro-aircraft use electromagnetic motors, which are difficult to adapt to complex electromagnetic environments and also produce certain noise when working.

[0003] The present invention utilizes a radial-bend composite sheet ultrasonic motor as the main body of the four-axis micro-aircraft, which has a simple and compact structure. Moreover, since the working principle of the ultrasonic motor is to utilize the vibration of the stator in the ultrasonic frequency band, the micro-aircraft is not afraid of electromagnetic interference, and since it works in the ultrasonic frequency band, the noise is also reduced. Summary of the invention

[0004] The embodiment of the present invention provides a four-axis micro-aircraft based on a radial-bend composite sheet-shaped ultrasonic motor. The aircraft can realize free flight in any direction, has a simple and compact structure, and is not subject to electromagnetic interference.

[0005] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0006] The embodiment of the present invention provides a four-axis micro-aircraft based on a radial-bend composite sheet ultrasonic motor, wherein the ultrasonic motor part includes: a stator 1, a piezoelectric ceramic 2, a rotor 3, an inner rotating shaft 4, a bearing 5, an outer rotating shaft 6, a spring 7, a large fixed 8, and a small fixed 9; wherein the stator 1 is outside, and the upper and lower parts of the rotor 3 are inside, and a hole is provided in the stator 1, and the inner rotating shaft 4 passes through the hole, and on one side of the stator 1, the upper half of the rotor 3, the spring 7, the large fixed 8, the outer rotating shaft 6, and the bearing 5 are sequentially mounted on the inner rotating shaft 4 from bottom to top, wherein the bearing 5 is installed inside the outer rotating shaft 6. On the other side of the stator 1, the lower half of the rotor 3, the spring 7, and the small fixed 9 are mounted on the inner rotating shaft 4 from top to bottom, and the preload of the spring is adjusted by adjusting the displacement of the large fixed 8 and the small fixed 9 on the inner rotating shaft 4, thereby controlling the pressure between the upper and lower parts of the rotor 3 and the stator 1.

[0007] The connecting part comprises: an annular base 11 and a cross beam 12, wherein the base 11 is used to fix the ultrasonic motor, and the cross beam 12 is used to connect four annular bases to form a whole.

[0008] As an implementation method, the outer rotating shaft 6 is connected to the upper part of the rotor 3 through the large fixing 8 and the spring 7. When the upper part of the rotor 3 rotates, the large fixing 8 is driven to rotate through the spring 7, thereby driving the outer rotating shaft 6 to rotate; the inner rotating shaft 4 is connected to the lower part of the rotor 3 through the spring 7 and the small fixing 9, and the rotation principle is similar to the former. The inner and outer rotating shafts realize completely independent rotation through the bearing 5 without interfering with each other, and the bearing 5 can also maintain the stability of the inner and outer rotating shafts in the vertical direction.

[0009] As an implementation mode, the stator 1 is a circular metal sheet containing a hollow convex cylinder inside and connected to its inner diameter through a beam waveguide structure. The upper and lower surfaces of the stator 1 have protruding hollow cylinders that contact the upper and lower parts of the rotor 3, and the pre-pressure between the two is adjusted by a spring 7.

[0010] As an implementation mode, the number of beams in the beam-type waveguide structure inside the stator 1 is designed according to needs, the shape of the beam can be a straight beam or a variable-section beam, and the beams in the beam-type waveguide structure inside the stator 1 are rotationally symmetric around the center of the stator.

[0011] As an implementation mode, the radial-bending composite sheet ultrasonic motor used in the micro-aircraft only uses a single piezoelectric ceramic 2 attached to the upper or lower surface of the stator 1. The inner diameter of the piezoelectric ceramic 2 is the same as that of the stator 1. The polarization direction is along the thickness direction. Any sine or cosine electrical signal is applied to the piezoelectric ceramic 2 to stimulate the first-order radial vibration and the third-order out-of-plane bending vibration of the stator 1. The use of a single piezoelectric ceramic is conducive to reducing the weight of the motor and reducing the heat generated by the motor, thereby extending the service life of the motor.

[0012] As an implementation mode, the rotors 10 used for the inner and outer shafts respectively use forward propellers and reverse propellers. The specific size and material are determined according to the actual situation. In principle, the lighter the better while ensuring the strength and rigidity.

[0013] As an implementation mode, the upper and lower parts of the rotor 3 are symmetrical hemispherical or conical.

[0014] As an implementation mode, when the radial-bending composite sheet ultrasonic motor used in the micro-aircraft is in working state, the piezoelectric ceramic 2 is polarized along the thickness direction, and a cosine Acos(wt+θ) or sine Asin(wt+θ) electrical signal is applied to the piezoelectric ceramic 2 through the electrode to stimulate the stator 1 to generate first-order radial vibration and out-of-plane third-order bending vibration, so as to realize the upper and lower rotors rotating in opposite directions, thereby driving the inner and outer rotating shafts to rotate in opposite directions.

[0015] As an implementation mode, the quad-axis micro-aircraft uses four identical radial-bend composite sheet ultrasonic motors fixed on the annular base 11, and the annular bases 11 are connected by the middle cross beam 12. The space provided by the cross beam can be used to arrange wires and place power and control systems. The specific shape of the cross beam is not required to be strictly vertical, and can also be an X shape.

[0016] As an implementation method, when the four-axis micro-aircraft is in working state, in order to facilitate the adjustment of the torque balance of the entire aircraft, the corresponding rotors of the A and C motors rotate in the same direction, the corresponding rotors of the B and D motors rotate in the same direction, but the corresponding rotors of the A and C motors and the B and D motors rotate in opposite directions.

[0017] As an implementation method, when the four-axis micro-aircraft is in the working state, by changing the magnitude of the voltage applied to the A, B, C, and D motors, and then changing the rotation speed of the rotating shaft, the lifting, pitching, and yaw functions of the aircraft can be realized. For example, when the voltage applied to the A, B, C, and D motors is increased at the same time, the lifting function can be realized; when the voltage of the B motor is increased and the voltage of the D motor is decreased, but the amount of change of the two motors is the same, and the voltage applied to the A and C motors remains unchanged, the pitch function can be realized; when the voltage of the A motor is increased and the voltage of the C motor is decreased, but the amount of change of the two motors is the same, and the voltage applied to the B and D motors remains unchanged, the rolling function can be realized; when the voltage applied to the A and C motors is decreased and the voltage applied to the B and D motors is increased, the yaw function can be realized by using the reverse torque (i.e., torque imbalance).

[0018] The four-axis micro-aircraft based on the radial-bending composite sheet ultrasonic motor provided by the embodiment of the present invention has good performance in both output torque and output speed, and is small in size, light in weight, compact in structure, fast in response, low in noise, and free from electromagnetic interference. It can be applied in complex electromagnetic environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic diagram of the structure of a radial-bend composite sheet-shaped ultrasonic motor provided by an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of a radial-bend composite sheet-shaped ultrasonic motor stator structure provided in an embodiment of the present invention;

[0022] Figure 3It is a schematic diagram of another radial-bend composite sheet-shaped ultrasonic motor stator structure provided by an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of the operation of a radial-bend composite sheet-shaped ultrasonic motor provided in an embodiment of the present invention;

[0024] Figure 5 A schematic diagram of a first-order radial vibration mode of a radial-bend composite sheet-shaped ultrasonic motor stator provided in an embodiment of the present invention;

[0025] Figure 6 A schematic diagram of an out-of-plane third-order bending vibration mode of a radial-bending composite sheet-shaped ultrasonic motor stator provided in an embodiment of the present invention;

[0026] Figure 7 A partial schematic diagram of a quad-axis micro aerial vehicle provided by an embodiment of the present invention;

[0027] Figure 8 This is a schematic diagram of the overall structure of a four-axis micro aerial vehicle provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0029] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0030] Example 1

[0031] This embodiment discloses a radial-bend composite sheet ultrasonic motor for use in a quad-axis micro-aircraft. Figure 1 As shown, the ultrasonic motor includes a stator 1, a piezoelectric ceramic 2, a rotor 3, an inner rotating shaft 4, a bearing 5, an outer rotating shaft 6, a spring 7, a large fixed sleeve 8, and a small fixed sleeve 9; wherein,

[0032] The stator 1 is outside, the rotor 3 is inside, and the upper and lower parts of the rotor 3 are respectively located inside the upper and lower sides of the stator; a hole is provided in the stator 1, and the inner rotating shaft 4 passes through the hole. On one side of the stator 1, the upper half of the rotor 3, the spring 7, the large fixed sleeve 8, the outer rotating shaft 6, and the bearing 5 are sequentially mounted on the inner rotating shaft 4 from bottom to top, wherein the bearing 5 is installed inside the outer rotating shaft 6. The outer rotating shaft 6 contacts the inner rotating shaft 4 through the bearing 5 and does not rotate with the inner rotating shaft 4;

[0033] On the other side of the stator 1, the lower part of the rotor 3, the spring 7 and the small fixed sleeve 9 are mounted on the inner rotating shaft 4 from top to bottom. The preload of the spring is adjusted by adjusting the displacement of the large fixed sleeve 8 and the small fixed sleeve 9 on the inner rotating shaft 4, thereby controlling the pressure between the upper and lower parts of the rotor 3 and the stator 1.

[0034] like Figure 1 As shown, the spring 7 is divided into two parts, the upper part, one end of the upper part of the spring contacts the top surface of the upper part of the rotor, and the other end contacts the bottom surface of the large fixed sleeve 8. The top surface of the large fixed sleeve 8 is connected to the outer rotating shaft 6 through the large fixed 8 and the spring 7 and the upper part of the rotor 3. When the upper part of the rotor 3 rotates, the large fixed sleeve 8 is driven to rotate through the spring 7, thereby driving the outer rotating shaft 6 to rotate.

[0035] One end of the lower spring contacts the bottom surface of the lower half of the rotor, and the other end contacts the top surface of the small fixed sleeve 9. The inner rotating shaft 4 is connected to the lower half of the rotor 3 through the lower spring 7 and the small fixed sleeve 9. When the lower half of the rotor 3 rotates, the small fixed sleeve 9 is driven to rotate by the spring; the rotation principle is similar to the former.

[0036] The inner and outer rotating shafts can realize completely independent rotation through the bearing 5 without interfering with each other. Meanwhile, the bearing 5 can also maintain the stability of the inner and outer rotating shafts in the vertical direction.

[0037] like Figure 2 , Figure 3 As shown, the stator 1 contains a hollow convex cylinder inside, and a beam waveguide structure and a circular metal sheet connected to the inner diameter thereof are arranged inside the stator 1, wherein the internal beam waveguide structure is symmetrical in center, and the specific shape of the beam can be a straight beam or a variable cross-section beam; the upper and lower surfaces of the stator (1) both have convex hollow cylinders that contact the lower upper and upper parts of the upper and lower parts of the rotor 3, and the preload between the two is adjusted by a spring 7. The beam waveguide structure arranged inside the stator 1 is symmetrical in center, and the specific shape of the beam can be a straight beam or a variable cross-section beam.

[0038] like Figure 4As shown, a single piezoelectric ceramic 2 is attached to the upper or lower surface of the stator 1, the inner diameter of the piezoelectric ceramic 2 is the same as the inner diameter of the stator 1, and the polarization direction is along the thickness direction. Any sine or cosine electrical signal is applied to the piezoelectric ceramic 2 to stimulate the first-order radial vibration and the third-order bending vibration out of the plane of the stator 1. The use of a single piezoelectric ceramic is conducive to reducing the weight of the motor and reducing the heat generated by the motor, thereby extending the service life of the motor.

[0039] The embodiment of the present invention provides a four-axis micro-aircraft based on a radial-bend composite sheet-shaped ultrasonic motor. The aircraft can realize free flight in any direction, has a simple and compact structure, and is not subject to electromagnetic interference.

[0040] Example 2

[0041] This embodiment provides a four-axis micro-aircraft based on a radial-bend composite sheet ultrasonic motor, such as Figure 7 , Figure 8 As shown, it includes four radial-bending composite sheet ultrasonic motors as mentioned above, and the radial-bending composite sheet ultrasonic motors are respectively fixed on annular bases 11, and the annular bases 11 are connected by the middle X-beam 12; the space provided by the X-beam can be used to arrange wires and place power supplies and control systems.

[0042] The inner and outer rotating shafts use positive propellers and reverse propellers respectively. The specific size and material are determined according to the actual situation. In principle, the lighter the better under the premise of ensuring strength and rigidity. The upper and lower parts of the rotor 3 are symmetrical hemispherical or conical.

[0043] Preferably, both the inner and outer rotating shafts are processed from titanium alloy, which ensures strength and rigidity while maintaining vertical stability by its own weight. The bearing 5 uses a 681 model miniature deep groove ball bearing, which meets the requirements of the inner and outer rotating shaft speeds.

[0044] The connection part between the ultrasonic motor and the aircraft body includes: an annular base 11 and a cross beam 12, wherein the base 11 is used to fix the ultrasonic motor, and the cross beam 12 is used to connect four annular bases to form a whole.

[0045] Preferably, the annular base 11 and the cross beam 12 are both processed with carbon fiber, and the two are bonded and fixed with a specific AB glue. The strength and rigidity of the carbon fiber meet the requirements, and the weight itself is very light, which is very suitable for use as a fuselage.

[0046] Preferably, the stator 1 is processed by titanium alloy and the surface is ground to facilitate the attachment of the piezoelectric ceramic 2 .

[0047] As an implementation method, the number of beams in the beam waveguide structure inside the stator 1 is designed according to the needs, and the shape of the beam can be a straight beam or a variable cross-section beam such as Figure 3 The beams in the beam waveguide structure inside the stator 1 are rotationally symmetric around the center of the stator.

[0048] Preferably, the number of beams inside the stator 1 is six, and the shape is a straight beam, which has good performance in both output speed and output torque.

[0049] As an implementation mode, the radial-bending composite sheet ultrasonic motor used in the micro-aircraft only uses a single piezoelectric ceramic 2 attached to the upper or lower surface of the stator 1. The inner diameter of the piezoelectric ceramic 2 is the same as that of the stator 1. The polarization direction is along the thickness direction. Any sine or cosine electrical signal is applied to the piezoelectric ceramic 2 to stimulate the first-order radial vibration and the third-order out-of-plane bending vibration of the stator 1. The use of a single piezoelectric ceramic is conducive to reducing the weight of the motor and reducing the heat generated by the motor, thereby extending the service life of the motor.

[0050] Preferably, the piezoelectric ceramic 2 is made of PZT-8 material, and the polarization direction is along the thickness direction.

[0051] As an implementation mode, the rotors 10 used for the inner and outer shafts respectively use forward propellers and reverse propellers. The specific size and material are determined according to the actual situation. In principle, the lighter the better while ensuring the strength and rigidity.

[0052] Preferably, the rotor 10 is made of carbon fiber, and uses a forward propeller and a reverse propeller, respectively, with a wingspan of about 15 cm, and the two are of the same size.

[0053] As an implementation mode, the upper and lower parts of the rotor 3 are symmetrical hemispherical or conical.

[0054] Preferably, the rotor 3 is made of alumina ceramic material, which is beneficial to improving the friction coefficient between the rotor and the stator and increasing the friction force.

[0055] Example 3

[0056] Based on the aircraft composed of the above motors, this embodiment also provides a control method for the aircraft, which is essentially a coordinated control of the four motors to achieve changes in the flight state, attitude, and speed of the aircraft. When the radial-bending composite sheet ultrasonic motor used in the micro-aircraft is in a working state, the piezoelectric ceramic 2 is polarized along the thickness direction, and a cosine Acos(wt+θ) or sine Asin(wt+θ) electrical signal is applied to the piezoelectric ceramic 2 through the electrode to excite the stator 1 to generate first-order radial vibration and out-of-plane third-order bending vibration, so that the upper and lower rotors can rotate in opposite directions, thereby driving the inner and outer shafts to rotate in opposite directions.

[0057] In the embodiment of the present invention, when the motor is running, P is the spring preload, M is the driving torque, such as Figure 4 The working principle is as follows: when the stator 1 moves upward due to out-of-plane vibration, the hollow convex cylinder on the upper surface contacts the upper rotor, and the hollow convex cylinder on the lower surface is separated from the lower rotor. At the same time, the beam waveguide structure applies radial force to the cylinder, generating a clockwise torque, driving the hollow convex cylinder on the upper surface to rotate clockwise, and driving the upper rotor to rotate clockwise through friction, thereby driving the outer rotating shaft 6 to rotate clockwise; Similarly, when the stator 1 moves downward due to out-of-plane vibration, the hollow convex cylinder on the upper surface of the stator is separated from the upper rotor, and the hollow convex cylinder on the lower surface is in contact with the lower rotor. At the same time, the beam waveguide structure applies radial force to the cylinder, generating a counterclockwise torque, causing it to rotate counterclockwise, and driving the lower rotor to rotate counterclockwise through friction, thereby driving the inner rotating shaft 4 to rotate counterclockwise. Therefore, within a complete motion cycle T, the upper and lower parts of the rotor 3 can rotate in opposite directions, and each cycle is T / 2.

[0058] In order to increase the displacement of the first-order radial vibration and the third-order out-of-plane bending vibration of the stator in the embodiment of the present invention, it is necessary to adjust the size of the stator so that the first-order radial vibration mode (such as Figure 5 ) Out-of-plane third-order bending vibration mode (such as Figure 6 ) The vibration frequencies are close to each other. When the vibration frequencies of the above two modes are close to each other, the stator 1 will be stimulated to move in a hybrid mode at this frequency.

[0059] In the embodiment of the present invention, the gain effect brought by the hollow convex cylinders on the upper and lower surfaces of the stator 1 is mainly to provide sufficient contact between the stator 1 and the upper and lower rotors 3. At the same time, the hollow convex cylinders can also be appropriately chamfered to increase the contact area between the stator 1 and the rotor.

[0060] When the quad-axis micro-aircraft is in working state, by changing the voltage applied to the four ultrasonic motors A, B, C, and D, and then changing the rotation speed of the rotating shaft, the lifting, pitching, rolling, yaw and other functions of the aircraft can be realized. For example, when the voltage applied to the A, B, C, and D motors is increased at the same time, the lifting function can be realized; when the voltage of the B motor is increased and the voltage of the D motor is decreased, but the amount of change of the two motors must be the same, and the voltage applied to the A and C motors remains unchanged, the pitch function can be realized; when the voltage of the A motor is increased and the voltage of the C motor is decreased, but the amount of change of the two motors must be the same, and the voltage applied to the B and D motors remains unchanged, the rolling function can be realized; when the voltage applied to the A and C motors is decreased and the voltage applied to the B and D motors is increased, the yaw function can be realized by using the reverse torque (i.e., torque imbalance).

[0061] The four-axis micro-aircraft based on the radial-bending composite sheet ultrasonic motor provided by the embodiment of the present invention has good performance in both output torque and output speed, and is small in size, light in weight, compact in structure, fast in response, low in noise, and free from electromagnetic interference. It can be applied in complex electromagnetic environments.

[0062] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0063] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A radial-bending composite sheet ultrasonic motor for a quad-axis micro-aircraft, characterized in that: It comprises a stator (1), a piezoelectric ceramic (2), a rotor (3), an inner rotating shaft (4), a bearing (5), an outer rotating shaft (6), a spring (7), a large fixed shaft sleeve (8), and a small fixed shaft sleeve (9); wherein: The stator (1) is outside and the rotor (3) is inside. The rotor (3) is divided into an upper part and a lower part, which are respectively located on the upper and lower sides of the stator. A hole is provided in the stator (1), and the inner rotating shaft (4) passes through the hole. On one side of the stator (1), the upper part of the rotor (3), the spring (7), the large fixed sleeve (8), the outer rotating shaft (6), and the bearing (5) are sequentially mounted on the inner rotating shaft (4) from bottom to top, wherein the bearing (5) is installed inside the outer rotating shaft (6). The outer rotating shaft (6) contacts the inner rotating shaft (4) through the bearing (5) and does not rotate with the inner rotating shaft (4). On the other side of the stator (1), the lower half of the rotor (3), the spring (7) and the small fixed sleeve (9) are mounted on the inner rotating shaft (4) from top to bottom, and the preload of the spring is adjusted by adjusting the displacement of the large fixed sleeve (8) and the small fixed sleeve (9) on the inner rotating shaft (4), thereby controlling the pressure between the upper and lower parts of the rotor (3) and the stator (1); The spring (7) is divided into an upper and a lower part. One end of the upper spring contacts the top surface of the upper half of the rotor, and the other end contacts the bottom surface of the large fixed sleeve (8). The top surface of the large fixed sleeve (8) is connected to the outer rotating shaft (6). When the upper half of the rotor (3) rotates, the large fixed sleeve (8) is driven to rotate by the spring, thereby driving the outer rotating shaft (6) to rotate. One end of the lower spring contacts the bottom surface of the lower half of the rotor, and the other end contacts the top surface of the small fixed sleeve (9). The inner rotating shaft (4) is connected to the lower half of the rotor (3) through the lower spring and the small fixed sleeve (9). When the lower half of the rotor (3) rotates, the small fixed sleeve (9) is driven to rotate by the spring. The inner and outer rotating shafts realize completely independent rotation through the bearings (5) without interfering with each other, and at the same time the bearings (5) maintain the stability of the inner and outer rotating shafts in the vertical direction; The stator (1) contains a hollow convex cylinder, and a beam waveguide structure and a circular ring metal sheet connected to the inner diameter thereof are provided inside the stator (1); the upper surface and the lower surface of the stator (1) both have convex hollow cylinders that contact the lower and upper parts of the upper and lower parts of the rotor (3), and the pre-pressure between the two is adjusted by a spring (7); The beam-type waveguide structure provided inside the stator (1) is centrally symmetrical, and the specific shape of the beam is a straight beam or a variable-section beam.

2. The radial-bending composite sheet ultrasonic motor for quad-axis micro-aircraft according to claim 1, characterized in that: A single piece of piezoelectric ceramic (2) is attached to the upper surface or the lower surface of the stator (1); the inner diameter of the piezoelectric ceramic (2) is the same as the inner diameter of the stator (1); the polarization direction is along the thickness direction; any sine or cosine electrical signal is applied to the piezoelectric ceramic (2) to excite the first-order radial vibration and out-of-plane third-order bending vibration of the stator (1).

3. The radial-bending composite sheet ultrasonic motor for a quad-axis micro-aircraft according to claim 1, characterized in that: The rotors (10) used for the inner and outer rotating shafts are respectively positive propellers and reverse propellers. The specific size and material are determined according to the actual situation. The lighter the better while ensuring the strength and rigidity. The upper and lower parts of the rotor (3) are symmetrical hemispherical or conical.

4. The working method of the radial-bending composite sheet ultrasonic motor applied to a quad-axis micro-aircraft according to any one of claims 1 to 3, characterized in that: When the ultrasonic motor is in a working state, the piezoelectric ceramic (2) is polarized along the thickness direction, and a cosine Acos(wt+θ) or sine Asin(wt+θ) electrical signal is applied to the piezoelectric ceramic (2) through an electrode, thereby stimulating the stator (1) to generate first-order radial vibration and third-order out-of-plane bending vibration, thereby realizing the upper and lower rotors rotating in opposite directions, thereby driving the inner and outer rotating shafts to rotate in opposite directions.

5. A quadcopter micro aerial vehicle, characterized in that: The aircraft comprises four radial-bending composite sheet ultrasonic motors as described in claim 1, wherein the radial-bending composite sheet ultrasonic motors are respectively fixed on annular bases (11), and the annular bases (11) are connected to each other through an intermediate X-beam (12); the space provided by the X-beam can be used for arranging wires and placing a power supply and a control system.

6. The quadcopter micro aerial vehicle according to claim 5, characterized in that: When the quadcopter micro-aircraft is in working state, the corresponding rotors of the two ultrasonic motors on the same line of the X-beam rotate in the same direction, the corresponding rotors of the two ultrasonic motors on the other line rotate in the same direction, and the corresponding rotors of the ultrasonic motors on different lines of the X-beam rotate in opposite directions.

7. The quadcopter micro aerial vehicle according to claim 5, characterized in that: When the four-axis micro-aircraft is in working state, the lifting, pitching, rolling and yaw functions of the aircraft can be realized by changing the magnitude of the voltage applied to the four ultrasonic motors and then changing the rotation speed of the rotating shaft.

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